fix: mcache skip manage > 1gb buffer

lang/mcache/mcache.go

@@ -20,13 +20,18 @@ import (
 	"github.com/bytedance/gopkg/lang/dirtmake"
 )
 
-const maxSize = 46
+const (
+	maxCachedIndex = 30 // len(caches) = maxCachedIndex+1
+
+	// mcache will never cache the buffer that out of maxCachedSize, which will cause high memory usage
+	maxCachedSize = 1 << maxCachedIndex // 1GB
+)
 
 // index contains []byte which cap is 1<<index
-var caches [maxSize]sync.Pool
+var caches [maxCachedIndex + 1]sync.Pool
 
 func init() {
-	for i := 0; i < maxSize; i++ {
+	for i := 0; i <= maxCachedIndex; i++ {
 		size := 1 << i
 		caches[i].New = func() interface{} {
 			buf := dirtmake.Bytes(0, size)
@@ -57,15 +62,20 @@ func Malloc(size int, capacity ...int) []byte {
 	if len(capacity) > 0 && capacity[0] > size {
 		c = capacity[0]
 	}
-	var ret = caches[calcIndex(c)].Get().([]byte)
+	if c > maxCachedSize {
+		return make([]byte, size, c)
+	}
+
+	sizeIdx := calcIndex(c)
+	var ret = caches[sizeIdx].Get().([]byte)
 	ret = ret[:size]
 	return ret
 }
 
 // Free should be called when the buf is no longer used.
 func Free(buf []byte) {
 	size := cap(buf)
-	if !isPowerOfTwo(size) {
+	if size > maxCachedSize || !isPowerOfTwo(size) {
 		return
 	}
 	buf = buf[:0]

lang/mcache/mcache_test.go

@@ -14,11 +14,34 @@
 
 package mcache
 
-import "testing"
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
 
 func TestMalloc(t *testing.T) {
-	buf := Malloc(4096)
-	t.Log(cap(buf))
+	// cached by mcache
+	size := 4096 - 1
+	buf := Malloc(size)
+	assert.Equal(t, len(buf), size)
+	assert.Equal(t, cap(buf), size+1)
+	_ = buf[:size+1] // resize
+	Free(buf)
+
+	// cached by mcache
+	size = 1024 * 1024 * 1024
+	buf = Malloc(size)
+	assert.Equal(t, len(buf), size)
+	assert.Equal(t, cap(buf), size)
+	Free(buf)
+
+	// not cached by mcache
+	size = 1024*1024*1024 + 1
+	buf = Malloc(size)
+	assert.Equal(t, len(buf), size)
+	assert.Equal(t, cap(buf), size)
+	Free(buf)
 }
 
 func BenchmarkNormal4096(b *testing.B) {